ok i have a question im really stuck on

for this i used the substitution u = x^3y and end up with but no matter how i rearrange it i cant separate the variables

Results 1 to 4 of 4

- Feb 14th 2010, 05:56 PM #1

- Joined
- Oct 2009
- From
- Aberystwyth, Wales
- Posts
- 36

- Feb 14th 2010, 06:12 PM #2

- Feb 14th 2010, 06:18 PM #3

- Joined
- Jul 2009
- Posts
- 593
- Thanks
- 4

Oh dear. Well, at least you recognize this as a linear first order differential. It is the confusion on what your integrating factor is that is the problem. Remember, a differential is in linear form when it is written as:

, with an integrating factor equal to .

Rewriting the equation so that it is in linear form we get:

Thus, our integrating factor is . From here you should see how things start to cancel out. If you need more help, post here.

- Feb 15th 2010, 09:58 AM #4
the ODE is already in the required form. if we do what you did, we'd end up with , and multiplying through by that brings us back to the original ODE! we don't need an integrating factor here, everything is already in a nice form. just continue as if you already found the integrating factor